Rett syndrome is an X‐linked neurodevelopmental disorder caused by mutation of Mecp2 gene and pri... more Rett syndrome is an X‐linked neurodevelopmental disorder caused by mutation of Mecp2 gene and primarily affects females. Glial cell dysfunction has been implicated in in Rett syndrome (RTT) both in patients and in mouse models of this disorder and can affect synaptogenesis, glial metabolism and inflammation. Here we assessed whether treatment of adult (5–6 months old) symptomatic Mecp2‐heterozygous female mice with N‐acetyl cysteine conjugated to dendrimer (D‐NAC), which is known to target glia and modulate inflammation and oxidative injury, results in improved behavioral phenotype, sleep and glial inflammatory profile. We show that unbiased global metabolomic analysis of the hippocampus and striatum in adult Mecp2‐heterozygous mice demonstrates significant differences in lipid metabolism associated with neuroinflammation, providing the rationale for targeting glial inflammation in this model. Our results demonstrate that treatment with D‐NAC (10 mg/kg NAC) once weekly is more effic...
Seminars in Thoracic and Cardiovascular Surgery, 2023
Hypothermic circulatory arrest is a protective technique used when complete cessation of circulat... more Hypothermic circulatory arrest is a protective technique used when complete cessation of circulation is required during cardiac surgery. Prior efforts to decrease neurologic injury with the NMDA receptor antagonist MK801 were limited by unacceptable side effects. We hypothesized that ketamine would provide neuroprotection without dose-limiting side effects. Canines were peripherally cannulated for cardiopulmonary bypass, cooled to 18°C, and underwent 90 minutes of circulatory arrest. Ketamine-treated canines (n=5; total dose 2.85 mg/kg) were compared to untreated controls (n=10). A validated neurobehavioral deficit score was obtained at 24, 48, and 72 hours (0=no deficits/normal exam; higher score represents increasing deficits). Biomarkers of neuronal injury in the cerebrospinal fluid were examined at baseline and at 8, 24, 48, and 72 hours. Brain histopathologic injury was scored at 72 hours (higher score indicates more necrosis and apoptosis). Ketamine-treated canines had significantly improved, lower neurobehavioral deficit scores compared to controls (overall p=0.003; 24 hours: median 72 vs. 112, p=0.030; 48 hours: 47 vs. 90, p=0.021; 72 hours: 30 vs. 89, p=0.069). Although the histopathologic injury scores of ketamine-treated canines (median 12) were lower than controls (16), there was no statistical difference (p=0.10). Levels of phosphorylated neurofilament-H and neuron specific enolase, markers of neuronal injury, were significantly lower in ketamine-treated animals (p=0.010 and =0.039, respectively). Ketamine significantly reduced neurologic deficits and biomarkers of injury in canines after hypothermic circulatory arrest. Ketamine represents a safe and approved medication that may be useful as a pharmacologic neuroprotectant during cardiac surgery with circulatory arrest.
BACKGROUND Hypothermic circulatory arrest (HCA) is associated with neurologic morbidity, in part ... more BACKGROUND Hypothermic circulatory arrest (HCA) is associated with neurologic morbidity, in part mediated by activation of the N-methyl-D-aspartate glutamate receptor causing excitotoxicity and neuronal apoptosis. Using a canine model, we hypothesized that the N-methyl-D-aspartate receptor antagonist MK801 would provide neuroprotection and that MK801 conjugation to dendrimer nanoparticles would improve efficacy. MATERIALS AND METHODS Male hound dogs were placed on cardiopulmonary bypass, cooled to 18°C, and underwent 90 min of HCA. Dendrimer conjugates (d-MK801) were prepared by covalently linking dendrimer surface OH groups to MK801. Six experimental groups received either saline (control), medium- (0.15 mg/kg) or high-dose (1.56 mg/kg) MK801, or low- (0.05 mg/kg), medium-, or high-dose d-MK801. At 24, 48, and 72 h after HCA, animals were scored by a standardized neurobehavioral paradigm (higher scores indicate increasing deficits). Cerebrospinal fluid was obtained at baseline, eight, 24, 48, and 72 h after HCA. At 72 h, brains were examined for histopathologic injury in a blinded manner (higher scores indicate more injury). RESULTS Neurobehavioral deficit scores were reduced by low-dose d-MK801 on postoperative day two (P < 0.05) and by medium-dose d-MK801 on postoperative day 3 (P = 0.05) compared with saline controls, but free drug had no effect. In contrast, high-dose free MK801 significantly improved histopathology scores compared with saline (P < 0.05) and altered biomarkers of injury in cerebrospinal fluid, with a significant reduction in phosphorylated neurofilament-H for high-dose MK801 versus saline (P < 0.05). CONCLUSIONS Treatment with MK-801 demonstrated significant improvement in neurobehavioral and histopathology scores after HCA, although not consistently across doses and conjugates.
It has been proposed repeatedly that the noradrenergic (NE) system may exert an influence on cort... more It has been proposed repeatedly that the noradrenergic (NE) system may exert an influence on cortical development. We have tested this proposition by examining synaptogenesis in the visual cortex of rats whose NE afferents were selectively lesioned by injections of the neurotoxin 6-hydroxydopamine (6-OHDA). Control littermates were injected with equal volumes of vehicle. Montages of electron micrographs covering approximately 50 micrometers-wide strips of cortex were assembled from both groups of animals at 2,4,6,8,14, and 90 days of age. Synapse counts revealed a significantly higher density of synapses in the cortex of 6-OHDA-treated rats during the first week of postnatal life. The difference between the experimental and control rats was less apparent during the second postnatal week, and at day 90 the densities of synapses were similar for the two groups of animals. The enhanced density, which was the result of the increased number of Gray&#39;s type I synapses, was confined to the subplate region at day 2 but became more widespread in the cortex at subsequent stages of development. From these observations it would appear that the NE system exerts an inhibitory influence on synapse formation in the visual cortex in early postnatal life.
The ontogeny of metabotropic excitatory amino acid receptors (mGluRs) in rat barrel field cortex ... more The ontogeny of metabotropic excitatory amino acid receptors (mGluRs) in rat barrel field cortex was characterized by using receptor autoradiography and immunocytochemistry to test the hypothesis that changes in mGluR expression coincide with the emergence of somatotopic patterns in this region. On postnatal days 1 (P1) and 3, [3H]glutamate binding to mGluRs was not distributed in a somatotopic pattern. By P5, mGluRs exhibited a whisker-related pattern, with higher densities of mGluRs in barrel centers than in surrounding cortex. Between P5 and P14 and at P60, the overall binding density remained higher in barrels than in surrounding cortex. At P60, a somatotopic pattern of binding was not apparent. The majority of mGluR sites in the barrel field were blocked by the metabotropic agonist trans-1-aminocyclopentane-1,3-dicarboxylic acid but were not significantly displaced by quisqualate. Immunocytochemical studies of phosphoinositide-linked mGluRs, mGluR5 and mGluR1alpha, showed that the developmental expression of mGluR5 mirrored that of the pattern of autoradiographically labeled mGluRs. The immature barrel field (ages P5-P14) was enriched in mGluR5, with greater concentrations of mGluR5 immunoreactivity in barrels than in surrounding cortex. Within barrel centers, mGluR5 was localized within the neuropil, on the surfaces of cell bodies and dendrites in layer IV. A somatotopic pattern of mGluR5 immunoreactivity persisted into adulthood, although the pattern was less pronounced after P14. In contrast, mGluR1alpha was never localized in a somatotopic pattern in barrel field cortex. We conclude from the developmental localization of mGluRs that the spatiotemporal regulated expression of these receptors may influence barrel maturation and plasticity.
Rett Syndrome (RTT) is a genetic disorder that is caused by mutations in the x-linked gene coding... more Rett Syndrome (RTT) is a genetic disorder that is caused by mutations in the x-linked gene coding for methyl-CpG-biding-protein 2 (MECP2) and that mainly affects females. Male and female transgenic mouse models of RTT have been studied extensively, and we have learned a great deal regarding RTT neuropathology and how MeCP2 deficiency may be influencing brain function and maturation. In this manuscript we review what is known concerning structural and coinciding functional and behavioral deficits in RTT and in mouse models of MeCP2 deficiency. We also introduce our own corroborating data regarding behavioral phenotype and morphological alterations in volume of the cortex and striatum and the density of neurons, aberrations in experience-dependent plasticity within the barrel cortex and the impact of MeCP2 loss on glial structure. We conclude that regional structural changes in genetic models of RTT show great similarity to the alterations in brain structure of patients with RTT. These region-specific modifications often coincide with phenotype onset and contribute to larger issues of circuit connectivity, progression, and severity. Although the alterations seen in mouse models of RTT appear to be primarily due to cell-autonomous effects, there are also non-cell autonomous mechanisms including those caused by MeCP2-deficient glia that negatively impact healthy neuronal function. Collectively, this body of work has provided a solid foundation on which to continue to build our understanding of the role of MeCP2 on neuronal and glial structure and function, its greater impact on neural development, and potential new therapeutic avenues.
BACKGROUND Hypothermic circulatory arrest (HCA) is associated with neurologic morbidity, in part ... more BACKGROUND Hypothermic circulatory arrest (HCA) is associated with neurologic morbidity, in part mediated by activation of the N-methyl-D-aspartate glutamate receptor causing excitotoxicity and neuronal apoptosis. Using a canine model, we hypothesized that the N-methyl-D-aspartate receptor antagonist MK801 would provide neuroprotection and that MK801 conjugation to dendrimer nanoparticles would improve efficacy. MATERIALS AND METHODS Male hound dogs were placed on cardiopulmonary bypass, cooled to 18°C, and underwent 90 min of HCA. Dendrimer conjugates (d-MK801) were prepared by covalently linking dendrimer surface OH groups to MK801. Six experimental groups received either saline (control), medium- (0.15 mg/kg) or high-dose (1.56 mg/kg) MK801, or low- (0.05 mg/kg), medium-, or high-dose d-MK801. At 24, 48, and 72 h after HCA, animals were scored by a standardized neurobehavioral paradigm (higher scores indicate increasing deficits). Cerebrospinal fluid was obtained at baseline, eight, 24, 48, and 72 h after HCA. At 72 h, brains were examined for histopathologic injury in a blinded manner (higher scores indicate more injury). RESULTS Neurobehavioral deficit scores were reduced by low-dose d-MK801 on postoperative day two (P < 0.05) and by medium-dose d-MK801 on postoperative day 3 (P = 0.05) compared with saline controls, but free drug had no effect. In contrast, high-dose free MK801 significantly improved histopathology scores compared with saline (P < 0.05) and altered biomarkers of injury in cerebrospinal fluid, with a significant reduction in phosphorylated neurofilament-H for high-dose MK801 versus saline (P < 0.05). CONCLUSIONS Treatment with MK-801 demonstrated significant improvement in neurobehavioral and histopathology scores after HCA, although not consistently across doses and conjugates.
Recent studies suggest that the cerebellum may have a significant role in repetitive behaviors. I... more Recent studies suggest that the cerebellum may have a significant role in repetitive behaviors. In primary complex motor stereotypies, typically developing children have repetitive movements usually involving rhythmic flapping/waving arm/hand movements. Similarly, the deer mouse animal model exhibits inherited repetitive behaviors, with increased frequencies of spontaneous jumping and rearing. In this study, data from both children with motor stereotypies and deer mice were used to investigate the role of the cerebellum in repetitive behaviors. The 3.0-T MRI volumetric imaging of the cerebellum was obtained in 20 children with primary complex motor stereotypies and 20 healthy controls. In deer mice, cerebellar volume (n = 7/group) and cell counts (n = 9/group) were compared between high- and low-activity animals. Levels of cerebellar neurotransmitters were also determined via HPLC (n = 10/group). In children with stereotypies, (a) there were a statistically significant reduction (compared to controls) in the white matter volume of the posterior cerebellar lobule VI-VII that negatively correlated with motor control and (b) an 8% increase in the anterior vermis gray matter that positively correlated with motor Stereotypy Severity Scores (SSS). In deer mice, (a) there was a significant increase in the volume of the anterior vermal granular cell layer that was associated with higher activity and (b) dentate nucleus cell counts were higher in high activity animals. Similar increases in volume were observed in anterior vermis in children with stereotypies and a deer mouse model of repetitive behaviors. These preliminary findings support the need for further investigation of the cerebellum in repetitive behaviors.
From a neurobiologic perspective, Rett syndrome appears to disrupt the growth of axonodendritic c... more From a neurobiologic perspective, Rett syndrome appears to disrupt the growth of axonodendritic connections among neurons. The cell packing density within the grey matter is increased but the total number of neurons is relatively normal, except for selected neuronal populations such as the nucleus basalis of Meynert (NBM) and the substantia nigra. Neurochemical assays of postmortem brain from patients with Rett syndrome patients demonstrate reductions in choline acetyltransferase (ChAT), the acetylcholine synthetic enzyme localized in NBM nerve terminals. In an animal model, early postnatal injury to the cholinergic pathways projected from the NBM causes permanent disruption of developing cholinergic neurons and a behavioral disorder on maze testing. The results suggest a mechanism by which early deficits in cholinergic and dopamine neurons projecting to the cerebral cortex from the brainstem and basal forebrain could disrupt axonodendritic development in the cerebral cortex. Studies in our laboratory are examining the mechanisms for these effects as well as the distribution and densities of neurotransmitter receptors in postmortem brains from Rett patients.
BACKGROUND Hypothermic circulatory arrest (HCA) is a technique used for complex repair of the aor... more BACKGROUND Hypothermic circulatory arrest (HCA) is a technique used for complex repair of the aorta, but it can be associated with neurologic morbidity. To better understand the molecular changes that underlie ischemic brain injury, we assessed gene expression and cytokine/chemokine polypeptide concentration in brain tissue and cerebrospinal fluid (CSF) of canines that underwent two hours of HCA. MATERIALS AND METHODS Adult male canines were cannulated peripherally for cardiopulmonary bypass, cooled to 18°C, and arrested for two hours. Animals were euthanized two, eight, or 24 hours post-HCA (n = 8 per group), and their brains were compared to brains from eight normal canines, using gene expression microarray analysis, cytokine assay, and histopathology. RESULTS Two to eight hours after HCA, pro-inflammatory cytokine mRNAs increased markedly, and gene expression was enriched within signaling pathways related to neuroinflammation or ischemic injury. Concentrations of pro-inflammatory cytokine polypeptides IL-6, IL-8, IL-1β, and CCL2 were very low in normal canine brain, whereas anti-inflammatory IL-10 and TGF-β1 were expressed at moderate levels. Pro-inflammatory cytokine concentrations rose robustly in cerebral tissue and CSF after HCA. IL-6 and IL-8 peaked at eight hours and declined at 24 hours, while IL-1β and CCL2 remained elevated. Concentrations of anti-inflammatory IL-10 and TGF-β1 were maintained after HCA, with a significant increase in TGF-β1 at 24 hours. CONCLUSIONS These cytokines represent potential diagnostic markers for ischemic neurologic injury that could be used to assess neurologic injury in patients undergoing HCA. The cellular mechanisms underlying this pro-inflammatory, ischemic-induced injury represent potential targets for neuroprotection in the future.
Rett syndrome is an X‐linked neurodevelopmental disorder caused by mutation of Mecp2 gene and pri... more Rett syndrome is an X‐linked neurodevelopmental disorder caused by mutation of Mecp2 gene and primarily affects females. Glial cell dysfunction has been implicated in in Rett syndrome (RTT) both in patients and in mouse models of this disorder and can affect synaptogenesis, glial metabolism and inflammation. Here we assessed whether treatment of adult (5–6 months old) symptomatic Mecp2‐heterozygous female mice with N‐acetyl cysteine conjugated to dendrimer (D‐NAC), which is known to target glia and modulate inflammation and oxidative injury, results in improved behavioral phenotype, sleep and glial inflammatory profile. We show that unbiased global metabolomic analysis of the hippocampus and striatum in adult Mecp2‐heterozygous mice demonstrates significant differences in lipid metabolism associated with neuroinflammation, providing the rationale for targeting glial inflammation in this model. Our results demonstrate that treatment with D‐NAC (10 mg/kg NAC) once weekly is more effic...
Seminars in Thoracic and Cardiovascular Surgery, 2023
Hypothermic circulatory arrest is a protective technique used when complete cessation of circulat... more Hypothermic circulatory arrest is a protective technique used when complete cessation of circulation is required during cardiac surgery. Prior efforts to decrease neurologic injury with the NMDA receptor antagonist MK801 were limited by unacceptable side effects. We hypothesized that ketamine would provide neuroprotection without dose-limiting side effects. Canines were peripherally cannulated for cardiopulmonary bypass, cooled to 18°C, and underwent 90 minutes of circulatory arrest. Ketamine-treated canines (n=5; total dose 2.85 mg/kg) were compared to untreated controls (n=10). A validated neurobehavioral deficit score was obtained at 24, 48, and 72 hours (0=no deficits/normal exam; higher score represents increasing deficits). Biomarkers of neuronal injury in the cerebrospinal fluid were examined at baseline and at 8, 24, 48, and 72 hours. Brain histopathologic injury was scored at 72 hours (higher score indicates more necrosis and apoptosis). Ketamine-treated canines had significantly improved, lower neurobehavioral deficit scores compared to controls (overall p=0.003; 24 hours: median 72 vs. 112, p=0.030; 48 hours: 47 vs. 90, p=0.021; 72 hours: 30 vs. 89, p=0.069). Although the histopathologic injury scores of ketamine-treated canines (median 12) were lower than controls (16), there was no statistical difference (p=0.10). Levels of phosphorylated neurofilament-H and neuron specific enolase, markers of neuronal injury, were significantly lower in ketamine-treated animals (p=0.010 and =0.039, respectively). Ketamine significantly reduced neurologic deficits and biomarkers of injury in canines after hypothermic circulatory arrest. Ketamine represents a safe and approved medication that may be useful as a pharmacologic neuroprotectant during cardiac surgery with circulatory arrest.
BACKGROUND Hypothermic circulatory arrest (HCA) is associated with neurologic morbidity, in part ... more BACKGROUND Hypothermic circulatory arrest (HCA) is associated with neurologic morbidity, in part mediated by activation of the N-methyl-D-aspartate glutamate receptor causing excitotoxicity and neuronal apoptosis. Using a canine model, we hypothesized that the N-methyl-D-aspartate receptor antagonist MK801 would provide neuroprotection and that MK801 conjugation to dendrimer nanoparticles would improve efficacy. MATERIALS AND METHODS Male hound dogs were placed on cardiopulmonary bypass, cooled to 18°C, and underwent 90 min of HCA. Dendrimer conjugates (d-MK801) were prepared by covalently linking dendrimer surface OH groups to MK801. Six experimental groups received either saline (control), medium- (0.15 mg/kg) or high-dose (1.56 mg/kg) MK801, or low- (0.05 mg/kg), medium-, or high-dose d-MK801. At 24, 48, and 72 h after HCA, animals were scored by a standardized neurobehavioral paradigm (higher scores indicate increasing deficits). Cerebrospinal fluid was obtained at baseline, eight, 24, 48, and 72 h after HCA. At 72 h, brains were examined for histopathologic injury in a blinded manner (higher scores indicate more injury). RESULTS Neurobehavioral deficit scores were reduced by low-dose d-MK801 on postoperative day two (P < 0.05) and by medium-dose d-MK801 on postoperative day 3 (P = 0.05) compared with saline controls, but free drug had no effect. In contrast, high-dose free MK801 significantly improved histopathology scores compared with saline (P < 0.05) and altered biomarkers of injury in cerebrospinal fluid, with a significant reduction in phosphorylated neurofilament-H for high-dose MK801 versus saline (P < 0.05). CONCLUSIONS Treatment with MK-801 demonstrated significant improvement in neurobehavioral and histopathology scores after HCA, although not consistently across doses and conjugates.
It has been proposed repeatedly that the noradrenergic (NE) system may exert an influence on cort... more It has been proposed repeatedly that the noradrenergic (NE) system may exert an influence on cortical development. We have tested this proposition by examining synaptogenesis in the visual cortex of rats whose NE afferents were selectively lesioned by injections of the neurotoxin 6-hydroxydopamine (6-OHDA). Control littermates were injected with equal volumes of vehicle. Montages of electron micrographs covering approximately 50 micrometers-wide strips of cortex were assembled from both groups of animals at 2,4,6,8,14, and 90 days of age. Synapse counts revealed a significantly higher density of synapses in the cortex of 6-OHDA-treated rats during the first week of postnatal life. The difference between the experimental and control rats was less apparent during the second postnatal week, and at day 90 the densities of synapses were similar for the two groups of animals. The enhanced density, which was the result of the increased number of Gray&#39;s type I synapses, was confined to the subplate region at day 2 but became more widespread in the cortex at subsequent stages of development. From these observations it would appear that the NE system exerts an inhibitory influence on synapse formation in the visual cortex in early postnatal life.
The ontogeny of metabotropic excitatory amino acid receptors (mGluRs) in rat barrel field cortex ... more The ontogeny of metabotropic excitatory amino acid receptors (mGluRs) in rat barrel field cortex was characterized by using receptor autoradiography and immunocytochemistry to test the hypothesis that changes in mGluR expression coincide with the emergence of somatotopic patterns in this region. On postnatal days 1 (P1) and 3, [3H]glutamate binding to mGluRs was not distributed in a somatotopic pattern. By P5, mGluRs exhibited a whisker-related pattern, with higher densities of mGluRs in barrel centers than in surrounding cortex. Between P5 and P14 and at P60, the overall binding density remained higher in barrels than in surrounding cortex. At P60, a somatotopic pattern of binding was not apparent. The majority of mGluR sites in the barrel field were blocked by the metabotropic agonist trans-1-aminocyclopentane-1,3-dicarboxylic acid but were not significantly displaced by quisqualate. Immunocytochemical studies of phosphoinositide-linked mGluRs, mGluR5 and mGluR1alpha, showed that the developmental expression of mGluR5 mirrored that of the pattern of autoradiographically labeled mGluRs. The immature barrel field (ages P5-P14) was enriched in mGluR5, with greater concentrations of mGluR5 immunoreactivity in barrels than in surrounding cortex. Within barrel centers, mGluR5 was localized within the neuropil, on the surfaces of cell bodies and dendrites in layer IV. A somatotopic pattern of mGluR5 immunoreactivity persisted into adulthood, although the pattern was less pronounced after P14. In contrast, mGluR1alpha was never localized in a somatotopic pattern in barrel field cortex. We conclude from the developmental localization of mGluRs that the spatiotemporal regulated expression of these receptors may influence barrel maturation and plasticity.
Rett Syndrome (RTT) is a genetic disorder that is caused by mutations in the x-linked gene coding... more Rett Syndrome (RTT) is a genetic disorder that is caused by mutations in the x-linked gene coding for methyl-CpG-biding-protein 2 (MECP2) and that mainly affects females. Male and female transgenic mouse models of RTT have been studied extensively, and we have learned a great deal regarding RTT neuropathology and how MeCP2 deficiency may be influencing brain function and maturation. In this manuscript we review what is known concerning structural and coinciding functional and behavioral deficits in RTT and in mouse models of MeCP2 deficiency. We also introduce our own corroborating data regarding behavioral phenotype and morphological alterations in volume of the cortex and striatum and the density of neurons, aberrations in experience-dependent plasticity within the barrel cortex and the impact of MeCP2 loss on glial structure. We conclude that regional structural changes in genetic models of RTT show great similarity to the alterations in brain structure of patients with RTT. These region-specific modifications often coincide with phenotype onset and contribute to larger issues of circuit connectivity, progression, and severity. Although the alterations seen in mouse models of RTT appear to be primarily due to cell-autonomous effects, there are also non-cell autonomous mechanisms including those caused by MeCP2-deficient glia that negatively impact healthy neuronal function. Collectively, this body of work has provided a solid foundation on which to continue to build our understanding of the role of MeCP2 on neuronal and glial structure and function, its greater impact on neural development, and potential new therapeutic avenues.
BACKGROUND Hypothermic circulatory arrest (HCA) is associated with neurologic morbidity, in part ... more BACKGROUND Hypothermic circulatory arrest (HCA) is associated with neurologic morbidity, in part mediated by activation of the N-methyl-D-aspartate glutamate receptor causing excitotoxicity and neuronal apoptosis. Using a canine model, we hypothesized that the N-methyl-D-aspartate receptor antagonist MK801 would provide neuroprotection and that MK801 conjugation to dendrimer nanoparticles would improve efficacy. MATERIALS AND METHODS Male hound dogs were placed on cardiopulmonary bypass, cooled to 18°C, and underwent 90 min of HCA. Dendrimer conjugates (d-MK801) were prepared by covalently linking dendrimer surface OH groups to MK801. Six experimental groups received either saline (control), medium- (0.15 mg/kg) or high-dose (1.56 mg/kg) MK801, or low- (0.05 mg/kg), medium-, or high-dose d-MK801. At 24, 48, and 72 h after HCA, animals were scored by a standardized neurobehavioral paradigm (higher scores indicate increasing deficits). Cerebrospinal fluid was obtained at baseline, eight, 24, 48, and 72 h after HCA. At 72 h, brains were examined for histopathologic injury in a blinded manner (higher scores indicate more injury). RESULTS Neurobehavioral deficit scores were reduced by low-dose d-MK801 on postoperative day two (P < 0.05) and by medium-dose d-MK801 on postoperative day 3 (P = 0.05) compared with saline controls, but free drug had no effect. In contrast, high-dose free MK801 significantly improved histopathology scores compared with saline (P < 0.05) and altered biomarkers of injury in cerebrospinal fluid, with a significant reduction in phosphorylated neurofilament-H for high-dose MK801 versus saline (P < 0.05). CONCLUSIONS Treatment with MK-801 demonstrated significant improvement in neurobehavioral and histopathology scores after HCA, although not consistently across doses and conjugates.
Recent studies suggest that the cerebellum may have a significant role in repetitive behaviors. I... more Recent studies suggest that the cerebellum may have a significant role in repetitive behaviors. In primary complex motor stereotypies, typically developing children have repetitive movements usually involving rhythmic flapping/waving arm/hand movements. Similarly, the deer mouse animal model exhibits inherited repetitive behaviors, with increased frequencies of spontaneous jumping and rearing. In this study, data from both children with motor stereotypies and deer mice were used to investigate the role of the cerebellum in repetitive behaviors. The 3.0-T MRI volumetric imaging of the cerebellum was obtained in 20 children with primary complex motor stereotypies and 20 healthy controls. In deer mice, cerebellar volume (n = 7/group) and cell counts (n = 9/group) were compared between high- and low-activity animals. Levels of cerebellar neurotransmitters were also determined via HPLC (n = 10/group). In children with stereotypies, (a) there were a statistically significant reduction (compared to controls) in the white matter volume of the posterior cerebellar lobule VI-VII that negatively correlated with motor control and (b) an 8% increase in the anterior vermis gray matter that positively correlated with motor Stereotypy Severity Scores (SSS). In deer mice, (a) there was a significant increase in the volume of the anterior vermal granular cell layer that was associated with higher activity and (b) dentate nucleus cell counts were higher in high activity animals. Similar increases in volume were observed in anterior vermis in children with stereotypies and a deer mouse model of repetitive behaviors. These preliminary findings support the need for further investigation of the cerebellum in repetitive behaviors.
From a neurobiologic perspective, Rett syndrome appears to disrupt the growth of axonodendritic c... more From a neurobiologic perspective, Rett syndrome appears to disrupt the growth of axonodendritic connections among neurons. The cell packing density within the grey matter is increased but the total number of neurons is relatively normal, except for selected neuronal populations such as the nucleus basalis of Meynert (NBM) and the substantia nigra. Neurochemical assays of postmortem brain from patients with Rett syndrome patients demonstrate reductions in choline acetyltransferase (ChAT), the acetylcholine synthetic enzyme localized in NBM nerve terminals. In an animal model, early postnatal injury to the cholinergic pathways projected from the NBM causes permanent disruption of developing cholinergic neurons and a behavioral disorder on maze testing. The results suggest a mechanism by which early deficits in cholinergic and dopamine neurons projecting to the cerebral cortex from the brainstem and basal forebrain could disrupt axonodendritic development in the cerebral cortex. Studies in our laboratory are examining the mechanisms for these effects as well as the distribution and densities of neurotransmitter receptors in postmortem brains from Rett patients.
BACKGROUND Hypothermic circulatory arrest (HCA) is a technique used for complex repair of the aor... more BACKGROUND Hypothermic circulatory arrest (HCA) is a technique used for complex repair of the aorta, but it can be associated with neurologic morbidity. To better understand the molecular changes that underlie ischemic brain injury, we assessed gene expression and cytokine/chemokine polypeptide concentration in brain tissue and cerebrospinal fluid (CSF) of canines that underwent two hours of HCA. MATERIALS AND METHODS Adult male canines were cannulated peripherally for cardiopulmonary bypass, cooled to 18°C, and arrested for two hours. Animals were euthanized two, eight, or 24 hours post-HCA (n = 8 per group), and their brains were compared to brains from eight normal canines, using gene expression microarray analysis, cytokine assay, and histopathology. RESULTS Two to eight hours after HCA, pro-inflammatory cytokine mRNAs increased markedly, and gene expression was enriched within signaling pathways related to neuroinflammation or ischemic injury. Concentrations of pro-inflammatory cytokine polypeptides IL-6, IL-8, IL-1β, and CCL2 were very low in normal canine brain, whereas anti-inflammatory IL-10 and TGF-β1 were expressed at moderate levels. Pro-inflammatory cytokine concentrations rose robustly in cerebral tissue and CSF after HCA. IL-6 and IL-8 peaked at eight hours and declined at 24 hours, while IL-1β and CCL2 remained elevated. Concentrations of anti-inflammatory IL-10 and TGF-β1 were maintained after HCA, with a significant increase in TGF-β1 at 24 hours. CONCLUSIONS These cytokines represent potential diagnostic markers for ischemic neurologic injury that could be used to assess neurologic injury in patients undergoing HCA. The cellular mechanisms underlying this pro-inflammatory, ischemic-induced injury represent potential targets for neuroprotection in the future.
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Papers by Mary Blue